The present disclosure relates to continuous board manufacturing processes and, more particularly, to an apparatus, system and method for the distribution of an aqueous gypsum slurry.
In a typical continuous gypsum manufacturing process, for example, a process such as those used to manufacture wallboard, water, calcined gypsum (i.e., stucco) and other additives as desired are combined and mixed in a pin mixer. Aqueous foam can be injected either in the mixer or outside the mixer to control the dry board density. Stucco is in the form of calcium sulfate hemihydrate and/or calcium sulfate anhydrite. The slurry is deposited onto a continuously advancing paper web moving on a conveyor. The slurry is allowed to spread over the advancing web of cover sheet material before a second web of cover sheet material is applied to cover the slurry and form a sandwich structure of a continuous wallboard preform, which is subjected to forming, such as at a conventional forming station, to obtain a desired thickness. The calcined gypsum reacts with the water in the preform and sets as the conveyor moves the preform down a manufacturing line. The preform is cut into segments at a point along the line where the preform has set sufficiently, flipped over, dried (e.g., in a kiln) to drive off excess water, and processed to provide the final wallboard product of desired dimensions.
The weight proportion of water relative to stucco that is mixed is referred to in the art as the “water-stucco ratio” (WSR). In the continuous wallboard production process industry, it is strongly desired to reduce the WSR to enhance manufacturing efficiency, for example, by reducing the energy required to dry the final products. However, a reduction of the WSR is not easily attainable. For example, slurry compositions having a higher water content have a lower viscosity, which can help spread the slurry across the width of the cover sheet web as it advances toward the forming station.
Prior apparatus and methods for addressing some of the operational problems associated with the production of gypsum wallboard are disclosed in commonly-assigned U.S. Pat. Nos. 5,683,635; 5,643,510; 6,494,609; 6,874,930; 7,007,914; and 7,296,919, which are incorporated herein by reference.